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LIBRARY OF CONGRESS, 


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Shelf TJAW 

- B 4 78 

UNITED STATES OF AMERICA. 























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The Tabor 


Steam Engine Indicator 


BY 


Geo. H. Barrus, S. B., 

r ( 

Member of the American Society of Mechanical Engineers. 







New York: 

Ashcroft Manufacturing Company. 

1884 . 





, B 


9 


Copyright 1883 by 

Ashcroft Manufacturing Company. 



/ 



Browne & Corlies, 
Steam Printers, 

108 Liberty St., New York. 


/ 









CONTENTS. 


PAGE. 

Chapter I. Introduction, ..... 7 

Chapter II. Description of the Tabor Indicator, . 9 

Chapter III. The Management and Care of the Tabor 

Indicator, ..... 13 

Chapter IV. The Essential Features of the Indicator 

Diagram, ..... 16 

Chapter V. The Uses to. which the Steam Engine 

Indicator may be applied, . . 18 

Chapter VI. The Use of the Indicator on Locomotive 

Engines, . . . . .30 

Chapter VII. The- Method of indicating a Steam 

Engine,.33 

ChapterVIII. The Method of computing the Horse 
Power of an engine from the Indicator 
Diagram, ..... 40 

Chapter IX. The Method of computing the amount of 

Steam accounted for by the Indicator, 46 
Chapter X. The Method of constructing the Hyper¬ 
bolic Curve, .... 50 

Chapter XI. Comparison between the performance of 
the Tabor Indicator and that of the 
Thompson and Richards Indicators, 51 
Table No. 1. Percentages of Cylinder Condensation, . 24 

Table No. 2. Feed-water consumption by Non-Con¬ 
densing Engines, ... 27 

Table No. 3. Feed-water consumption by Condensing 

Engines, . . . . .28 

Table No. 4. Areas of Circles.67 

Table No. 5. Weights of Saturated Steam at various 

pressures, and other quantities, . 71 











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PREFACE. 


/ ’J'' HESE pages were prepared at the solicitation of the 
Ashcroft Manufacturing Company, makers of the 
Tabor Indicator. They were not designed as an advertise¬ 
ment of the instrument but as a book of reference and 
instruction for purchasers and others interested in the subject. 

The table of engine performance, given in Chapter V., is 
offered in the hope of drawing attention to the value of 
feed-water tests of engines as opposed to simple indicator 
tests. It is given with some reluctance, however, owing to the 
scarcity of data on the subject of cylinder condensation. The 
allowances for this source of waste are assumed, but they 
correspond with those found in the author’s practice and are 
therefore believed to be not far from correct. 

In this connection the formula for computing the “ steam 
accounted for by the indicator,” which is new, will be found 
serviceable. 

To add interest to the subject, the results of an investigation 
are given in Chapter XI., in which the performance of the 
Tabor indicator is compared with that of the old pattern 
Thompson and the Richards indicators, and the advantages of 
reducing the weight of the moving parts to a minimum are 
shown. As one of the last named instruments has been 
improved, and the other is almost out of use, this compari¬ 
son will not be regarded as an attempt to depreciate the 
instruments made by competing manufacturers. 

GEO. H. BARRUS, 
Engineer , 


81 Milk St., Boston, June 15, 1883, 



THE TABOR INDICATOR 

































































































































































The Tabor Indicator 


CHAPTER I. 

INTRODUCTION. 

'T'HE Steam Engine Indicators that have come into prominent 
use in this country have one essential plan of construction. 
There is a steam cylinder and a paper drum. The steam cylinder 
is designed to connect with the interior of the engine cylinder 
and receive steam whenever the engine receives it. A piston, 
which is enclosed, communicates motion to a pencil arranged 
to move in a straight line, the amount of whose movement is 
limited by the tension of a spiral spring against which the 
piston acts. The paper drum is a cylindrical shell mounted on 
its axis and is made to turn forward and backward by a motion 
derived from the cross-head of the engine. A sheet of paper 
or card , as it is named, is stretched upon the drum, and the 
pencil is brought to bear upon it. In this manner the instru¬ 
ment traces upon the paper a line termed the indicator diagram, 
which is the object sought. Since the motion of the card is 
made to coincide with that of the piston of the engine, and the 
•height to which the pencil rises varies according to variations 
in the force of the steam, the indicator diagram presents a 
record of the pressure of steam in the engine cylinder at every 
point of the stroke. 

To obtain well defined diagrams with instruments of this 
description, it has been found desirable to employ a spring of 



8 


THE TABOR INDICATOR. 


high tension so as to permit but a small movement of the piston. 
That a suitable height of the diagram may be obtained, this 
plan requires the multiplication of the movement of the piston. 
In the means that are employed for accomplishing this result, 
still preserving a straight line movement, the various forms of 
indicators that have been extensively used find their essential 
differences. 

The Richards Indicator, the first instrument of this kind that 
came into use, depends for the multiplication of the movement 
upon two levers, pivoted at opposite ends, and connected by a 
bar carrying the pencil. One of the levers at a point near the 
pivoted end receives the motion of the piston. The use of this 
indicator upon engines running at high speed showed that the 
momentum of the multiplying device produced a disturbance 
in the action of the instrument which made the diagram inac¬ 
curate. The Thompson Indicator following upon the Richards 
instrument, accomplished the straight line movement by a 
single lever and a system of links at the pivoted ends. The 
weight of the parts in the region of the pencil was thus greatly 
reduced and the instrument became better fitted for accurate 
work, not only on high speed engines but on those running at 
moderate speeds. 

The Tabor Indicator following upon the Thompson instru¬ 
ment, belongs to the same class. It was invented in 1879 by 
Mr. Harris Tabor, of Corning, N. Y., now Superintendent of 
the Westinghouse Machine Co., Pittsburgh, Penn. The object 
sought by Mr. Tabor, was to better adapt the instrument to the 
attainment of smooth and accurate diagrams at high speeds. 
He endeavored to provide a movement, having such few parts 
and those of such light weight, that a quick response to the 
action of the steam pressure should occur at any speed liable 
to be met in practice. The employment of high speeds is now 
of frequent occurrence on stationary engines and suitable pro¬ 
visions for indicating in those cases has become a recognized 
necessity. 


THE TABOR INDICATOR, 


9 


CHAPTER II. 

DESCRIPTION OF THE TABOR INDICATOR. 

'I'HE peculiarity of the Tabor Indicator lies in the means 

employed to communicate a straight line movement to 
the pencil. The rod which forms the connection between the 
piston and the pencil bar contains a curved slot. A roller turn¬ 
ing on a small pin located in the cover, passes through the 
slot and serves to guide the rod to one side or the other of a 
central position. The slot is curved to such a shape, that as 
the rod rises and falls, the pencil- is moved a sufficient 
amount to compensate for its tendency to travel in a circular 
arc, and a straight line motion results. 

The pencil bar is connected by means of the back link to a 
sleeve which encircles the top of the cylinder. The sleeve 
may be turned by the handle so as to bring the pencil into 
contact with the paper drum as is done in the act of taking a 
diagram. To enable the piston rod also to turn when this is 
done, a ball and socket connection is employed between the 
bottom of the rod and the piston, and the roller is mounted 
within a circular roller plate loosely encased in the cover. 
Attached to a projection on the side of the sleeve opposite the 
handle is a screw, which may be adjusted so as to strike 
against a stop on the frame of the indicator, and prevent the 
application of the pencil with too great force. The pressure 
upon the paper may by its use be made uniform, which secures 
the tracing of a line of uniform character. The piston travels 
in an inside cylinder screwed at the lower end to the main 
cylinder, which forms a part of the frame. Openings in the 


10 


THE TABOR INDICATOR. 


sides of the outer one allow the steam which leaks by the 
piston to escape. A plain coupling connects the instrument 
to the indicator cock. 

These parts are represented in the accompanying figure 
No. 1 showing the interior of the indicator, and in the frontis¬ 
piece. 

SECTIONAL ELEVATION OF THE TABOR 
INDICATOR. 



Figure No. 1. 






















THE TABOR INDICATOR. 


11 


Here are shown also the paper drum, held by a stud ; the 
spool on which the drum is mounted having at the bottom a 
groove for the driving cord ; the receptacle for the coiled spring 
which encircles the spindle and pulls the drum backward after 
the cord has drawn it forward; and the arm under the frame 
which holds the carrier pulleys and by the adjustment of which 
the motion of the driving cord may be received from any direc¬ 
tion. These are modifications of similar devices which have 
become familiar by their employment in other indicators. 

The spring used in the Tabor Indicator is made of two spiral 
coils of wire with necessary fittings as shown in Figure No. 2. 


THE DUPLEX SPRING. 



Figure No. 2. 


The upper fitting has a thread on the outside which attaches it 
to the under side of the cover. The lower fitting has a thread 
on the inside which screws upon the piston. At both ends the 
spring is so mounted that the points of connection of the two 
coils lie on opposite sides of the fitting. As the piston depends 
for a guide upon the cylindrical surface alone, it is important 
that there be a uniform strain upon it when under compression 
or tension, and the duplex arrangement is intended to meet this 
requirement. Instead of the rigid connection between the 
piston and spring, a ball joint is sometimes employed which 







the tabor Indicator. 


10 

1 


takes the place of the lower fitting. The faults produced by 
improperly mounted springs, or by those which have been 
sprung from correct position by improper use, are counter¬ 
acted by the employment of this device. 

The piston rod and pencil bar are made of steel, hardened 
and drawn to a spring temper. The end of the pencil bar is 
shaped in the form of a thin tube for the reception of the 
pencil lead. Being split apart on the side it yields to the 
slight pressure required to introduce the lead and holds it 
securely. The pencil lead and the stop screw are reversible 
and the position of the paper drum may be changed so that 
the pencil bar may be used on either side of the paper drum as 
convenience in operating may requii'e. The pencil movement 
multiplies the motion of the piston four times. The roller 
and pins at the joints ai*e made of steel and hardened. The 
cylinder and piston are made of composition. Their diameter 
is 0.7978 inch. The springs are made of Stub’s steel wire, 
attached to the fittings with hard solder, and they are coated 
with nickel plating. The diameter of the wire used in a 40 
spring is 0.073 inch. The correctness of the springs is proved 
under the action of a direct steam pressui'e. The paper drum 
is 2yg- inches in diameter, and has a motion fiom one exti'eme 
to the other of 5^ inches. 

In the manufacture of the Tabor Iixdicator two pi*ominent 
objects are kept in view, They are accuracy of construction 
and lightness in weight of the moving pai'ts, and they are 
secured by the use of the best tools in the hands of skilful 
mechanics. The reduction in the weight of the moving parts 
to^the smallest amount consistent with strength is readily 
secured with accurate consti'uction where its attainment would 
ofiiei'wise prove difficult. 

n< ^he relative weights of the moving pai'ts in the Tabor Indi¬ 
cator compared with those in the Richards and Thompson 
mslruments, referred to in the introduction, are given in the 
following table: 


THE TABOR INDICATOR. 


13 



Rich¬ 

ards. 

Thomp¬ 

son. 

Tabor. 

Weight of piston and rods directly 

Oz. 

Oz. 

Oz. 

attached to it, 

Weight of No. 40 spring, 

Weight of back link (in Thompson 

1.07 

.96 

.55 

.87 

.92 

.71 

and Tabor), ..... 
Weight of pencil bar (including in 
Richards and Thompson the rods 


.49 

.13 

which it carries), .... 

* .76 

.22 

.05 

Total weight of movement, 

2.70 

2.59 

1.43 

Weight of spool and paper drum, 

21.09 

15.82 

7.74 


* The parallel bars in the Richards Indicator referred to are 
double. 


CHAPTER III. 

THE MANAGEMENT AND CARE OF THE TABOR 
INDICATOR. 

HTHE attachment and changing of springs may be facilitated 
by observing the following directions : 

To attach a spring, remove the cover and the sleeve from 
the cylinder, taking with them the piston and the pencil 
movement. Disconnect the piston, and screw the spring into 
place on the bottom of the cover. Start the piston upon the 
lower end of 4 the spring two or three threads, and bring the 
ball-nut enclosing the end of the piston rod down into position, 
by the use of the small wrench accompanying the indicator, 
which is introduced between two adjacent coils of the spring. 














THE TARoR INDICATOR. 


n 


Hold against the end of the socket and catch the 

threacl lpy*i38?efully turning the piston. The wrench is then 
kept-st-^tTon^ryj, and the nut and rod brought into place by 
continued 'turning of the piston, after which the wrench may 
'l^remcm^d and the piston screwed up to its final position. 

HTo rejiStove a spring, the order of procedure is to be reversed. 
The piston should be loosened before starting the spring from 
t^e‘cover. * To do this, the spring may be held most securely 
by grasping it above the sleeve. The wrench is then intro- 
cfiObed afifl. the cITall-nut held stationary, while the piston is 
s^e^ed!^.^vay fiQton it, after which the piston and spring may 
be remoyed at once. 

The tension of the spring that may be employed in any case 
d^eftd^HfjS^T the maximum pressure to which it is to be 
subjected. In the following table the maximum pressures, 
measured above the atmosphere, to which various springs are 
adapted, are given, all of them being suitable for use on 
condensing cylinders: 


Number or Tension 
of Spring. 

SO' 

Maximum Pressure to which 
the Spring can be 
subjected. 

10 

14 

12 

20 

ban 16 

30 

20 

40 

(r 24 

48 

r 30 

60 

1 32 

64 

40 

80 

48 

96 

50 

100 

60 

120 

64 

128 

80 

, 160 

100 

200 


















THE TABOR INDICATOR. 


15 


A spring may be used, if desired, for pressures that are less 
than the limit ; but as a rule the lightest spring that can safely 
be employed is to be preferred, since the higher diagram that 
it produces is the more accurately measured. For engines 
running at high speeds the higher the tension of the spring the 
smoother the line of the diagram. It is for the operator to 
judge how far one object shall be sacrificed to the attainment 
of the other. 

In the care of the Tabor Indicator it is essential that there 
be perfect freedom in the movement, and especially in the 
motion of the piston. When not encumbered with a spring, 
the pencil bar, on being raised to its highest position, should 
freely drop to its lowest. In practical use, the cover and 
movement should from time to time be removed, and the 
rubbing surfaces of the piston and cylinder cleaned with a 
piece of waste or cotton cloth. On being replaced, the out¬ 
side of the piston should be well lubricated with valvoline or 
some other efficient cylinder oil. Before the cover is screwed 
on the piston may be moved up and down a short distance by 
raising the cover, and undue friction by this means may be 
detected. The bearings of the moving parts do not need so 
frequent lubrication as the rubbing surface of the piston. 
They should be oiled, when occasion requires, with watch 
oil or some light oil of good quality. 

The spring should be removed when the indicator is not in 
use. When allowed to remain the threads are liable to stick 
and it becomes difficult to start the piston from the spring. 

In order to obtain suitable diagrams the pencil lead should 
be kept well sharpened. It is best to remove it from its place 
for this purpose by crowding it out from the blunt end, and 
sharpen by using a knife or a fine file. 


16 


THE TABOR INDICATOR. 


CHAPTER IV. 


THE ESSENTIAL FEATURES OF THE INDICATOR 
DIAGRAM. 


'T'HE shape of the figure traced upon the Indicator card 
depends altogether upon the manner in which the steam 



Figure No. 3. 


pressure acts in the cylinder. If the steam be admitted at the 
beginning and exhausted at the end of the stroke and admission 
continue from one end to the other, the shape of the diagram 
is nearly rectangular. If the admission continue through only 
, a part of the stroke, the diagram assumes a shape similar to 
that of figure No. 3. These two representative forms have in 
matters of detail numberless modifications. 





THE TABOR INDICATOR. 


17 


Figure No. 3 has been taken to illustrate the essential 
features of the indicator diagram, because it exhibits clearly 
all the operations affected by pressure that commonly take 
place in the steam engine cylinder. 

This diagram shows that the admission of steam commences 
at A and ends at D ; the cut-off commences at C and becomes 
complete at D ; expansion occurs from D to E ; the release or 
exhaust begins at E and continues to the point H ; the com¬ 
pression of the exhaust steam commences at G and ends at the 
admission point. 

The line A B is called the admission line ; B C, the steam 
line ; D E, the expansion line ; F G, the exhaust or back pressure 
line (or, in the case of condensing engines, the vacuum line) ; H 
A, the compression line ; and J I, the atmospheric line. The 
curve which joins two adjacent lines, represents the action ot 
the steam when one operation changes to another and cannot 
properly be classed with either line. 

The point of cut-off, D, lies at the end of admission ; the 
point of release, E, at the beginning of the exhaust, the point 
of compression, H. at the end of the exhaust. The proportion 
of the whole length of the diagram borne by the distance of 
the point D from the admission end, represents the proportion 
of the stroke completed at the point of cut-off, so also in the 
case of the point of release, and in that of compression for the 
uncompleted portion of the stroke. The pressures at the points 
of cut-off, release and compression are the heights of these 
various points above the atmospheric line measured on the 
scale of the spring. 


18 


THE TABOR INDICATOR. 


CHAPTER V. 

THE USES TO WHICH THE STEAM ENGINE INDICATOR 
MAY EE APPLIED. 

' I "'HERE are three purposes for which the indicator diagram 
may be employed : 

First. To serve as a guide in setting the valves of an engine 

Second. To determine the indicated power developed by 
an engine. 

Third. To determine in connection with a feed-water test 
showing the actual amount of steam consumed, the economy 
with which an engine works. 

First. Figure No. 8 given in the last chapter shows the gen¬ 
eral features of a well formed indicator diagram, the attainment 
of which should be the aim in setting the valves of an engine. 
The admission of steam is prompt, making the admission line 
perpendicular to the atmospheric line ; the initial pressure is 
fully maintained up to the point where the steam begins to be 
cut off; the somewhat early release secures a free exhaust and 
a uniformly low back pressure ; and the exhaust valve closes 
before the return stroke is completed, providing for compression. 
These are the first requirements to be met. in producing an 
economical engine. Derangement of the valve gearing is 
revealed in the diagram by tardy admission or release, by low 
initial pressure or high back pressure or by absence of compres¬ 
sion, either one of which causes an increased consumption of 
steam for performing the same amount of work. Defects of 
this kind are illustrated by diagrams No. 1 and No. 2 which 
are reduced copies of some taken from an automatic cut-off 
engine; the fixst, when the valves were operated in their most 


THE TABOR INDICATOR. 


19 


efficient manner ; the second, after the main eccentric had been 
turned backward on the shaft 43 degrees. Here the faulty 
adjustment distorted every line of the diagrams. 


BEFORE SETTING THE ECCENTRIC BACKWARD 



Diagram No. 1. 


AFTER SETTING THE ECCENTRIC BACKWARD. 



Diagram No. 2 . 







20 


THE TABOR INDICATOR. 


The admission does not commence till the piston has 
travelled about one-sixteenth of the stroke. The release is 
also late by a similar amount. The maximum pressure before 
cut-off is comparatively low, the average back pressure is high, 
and there is entire absence of compression. ♦ 

The angular position of an eccentric controls all the move¬ 
ments of the valves, but improper lengths of the connecting 
rods which operate them, or improper proportions of lap and 
lead, are liable to produce faults similar to those shown in the 



Diagram No. 3. 


illustration. The waste of steam that was induced in this case 
is seen by a glance at the terminal point of the expansion line, 
which is very high in No. 2 compared with No. 1. 

In regulating the exhaust of an engine, the desirability of 
employing compression should not be overlooked. In the 
first place, it serves to overcome the momentum of the recipro¬ 
cating parts and to reduce the strain upon the connections 
caused by the sudden application of the pressure at admission. 
The jar caused by sudden admission is revealed by the effect it 
produces upon the indicator diagram. This is illustrated by 




THE taTor Indicator. 


21 

Diagram No. 3, which was taken from the same engine that 
gave those already referred to. The eccentric had in this case 
been turned backward 27° from the position it occupied when 
No. 1 was taken. The vibrations produced in No. 3 are very 
noticeable compared with the smoothness of No. 1. 

In the second place, compression is desirable on the ground 
of economy in the consumption of steam. It fills the wasteful 
clearance spaces of the cylinder with exhaust steam, otherwise 
requiring the expenditure of live steam from the boiler. 
Compression produces a loss by this increased back pressure 
which it occasions, but the loss is more than covered by 
the gain resulting from the reduction of clearance waste. 
Theoretically, the greater the amount of exhaust that is utilized 
by compression, the less the consumption of steam. Practically, 
it is not advisable to compress above the boiler pressure. In a 
non-condensing automatic cut-off engine with 3 per cent, clear¬ 
ance, working under 75 lbs. boiler pressure, cut off at one-fifth 
of the stroke, and exhausting under a minimum back pressure, 
the gain produced by compressing up to boiler pressure over 
working under the same conditions without compression, 
should be not less than six per cent. 

The valves being in proper adjustment, the indicator diagram 
shows whether the pipe and passages for the admission and 
exhaust of the steam are of sufficient size. In automatic cut-off 
engines the admission line should be parallel with the atmos¬ 
pheric line, and the initial pressure should not be more than 3 
lbs. less than the boiler pressure. The back pressure should 
not in any engine exceed 1 lb. when the exhaust proceeds 
directly to the atmosphere. 

Before making adjustments upon engines that have been 
long in use, the operator should ascertain whether a 
valve which should travel in a different place, has worn to a 
shoulder upon its seat. If changed under such circumstances, 
loss from leakage may follow, sufficient in amount to neutralize 
the saving that might otherwise result. 


22 


THE TABOR INDICATOR. 


Second. The indicator may be used to determine the amount 
of power developed by an engine. The diagram reveals the 
force of the steam at every point of the stroke. The power is 
computed from the average amount of this force, which is 
independent either of the adjustment of the valves, the form of 
the diagram'or of any condition upon which economy depends. 
The diagram gives what is termed the indicated power of an 
engine, which is the total power exerted by the steam. It 
includes both the effective power delivered and that consumed 
in propelling the engine itself. 

In this connection the indicator proves invaluable for meas¬ 
uring the amount of power transmitted to a machine or set of 
machines which the engine is employed to drive. The process 
consists in indicating the engine, first, with the machinery in 
operation, and then with the driving belt or shaft thrown off. 
The difference in the amount of power developed in the two 
cases is the desired result. Tenants and those who let power 
frequently employ the indicator for this purpose. 

The method of computing the power from the diagram is 
given in Chapter VIII. 

Third. The indicator may be used in connection with a 
feed-water test to determine the number of pounds of steam 
consumed by an engine per indicated horse power per hour. 

This forms a measure of the performance of an engine, and 
when compared with the performance of the best of its class 
shows the economy with which the engine works. The amount 
of steam consumed is usually found by weighing the feed- 
water before it is supplied to the boiler, the steam being 
employed during the test for no other purpose than driving the 
engine. As this requires the erection of weighing apparatus, a 
simpler plan may be resorted to, which, though less accurate, 
gives quite satisfactoiy results. The feed-water may be brought 
to a high point on the glasses and then shut off, and a test 
made by observing the rate at which the water boils away. 


THE TABOR INDICATOR. 


23 


A fall of six inches may be allowed in nearly every case with¬ 
out again feeding. The heights at the beginning and the end 
of the test being carefully observed, the amount of water evap¬ 
orated and supplied to the engine may be computed from the 
cubical contents that it occupied in the boilers. A test made 
in this manner can be a number of times repeated, and the 
results averaged, to insure greater accuracy. 

A portion of the consumption may be found without the aid 
of a feed-water test, by computation of the diagram. A method 
of making the calculation is given in Chapter IX. Were it 
not for losses produced by leakage and cylinder condensation, 
to which engines are subject, the whole amount of steam 
consumed might be determined in this manner. Leakage of 
steam sometimes occurs and cylinder condensation is inevita¬ 
ble, while the extent to which they act is not revealed by any 
marked effect produced upon the lines of the diagram. The 
measurement of the consumption of steam by diagram, therefore, 
cannot be taken to show actual performance without allowing 
a margin for these losses. Much value, however, often attaches 
to these computations. In the case for example of Diagram No. 
2, the waste of steam produced by the valve derangement would 
be shown quite as well by a comparison of the steam consump¬ 
tion by diagram in the two cases, as by a comparison of the 
feed-water consumptions. The result would doubtless be 
inaccurate, but near enough to the truth for practical uses. 

Besides showing the economy of an engine compared with 
the best of its class, the indicator reveals the extent of the losses 
produced by leakage and cylinder condensation. These losses 
are represented by that part of the feed-water consumption 
which remains after deducting the steam computed from the 
diagram or steam accounted for by the indicator , as it is 
termed. 

One of these losses, condensation, is nearly constant for 
different engines working under similar conditions,, and an 
allowance may be made for its amount. The other, leakage, is 


24 


TH£ TAhOk INDICATOR. 


variable in different cases depending upon the conditon of the 
wearing surfaces of valves, piston and cylinder. The fact of 
the presence of the latter may be detected by a trial under 
boiler pressure with engine at rest, the leakage being revealed 
by escape at the indicator cock. The extent of its action may 
be found by computing that part of the loss not covered by 
condensation. In other words, in the case of leaking engines, 
when the indicator and feed-water test show that there is more 
loss than is produced in good practice by condensation, the 
excess represents the probable amount of loss by leakage. The 
indicator thus finds a valuable use in connection with the feed- 
water test. To make it more available in practice, Table No. 1 
is appended, showing the percentages of loss that occur from 
cylinder condensation. These quantities apply to that type of 
factory engine that is commonly used in this country, that is, to 
unjacketed engines having cylinders exceeding 20 inches in 
diameter, and supplied with dry but not superheated steam. 
As elsewhere stated these quantities are assumed, but they 
conform to such experimental data as the writer has at hand 
applicable to the subject. 


TABLE No- 1. 

PERCENTAGES OF LOSS BY CYLINDER CONDENSATION. 


Percentage of Stroke completed 
at Cut-off. 

Cylinder Condensation at Cut-off. 
Percentage of whole consumption 
of feed water. 

5 

42 

10 

34 

15 

29 

20 

26 

30 

22 

40 

18 

50 

14 








THE TABOR INDICATOR. 


25 


In this connection, Tables No. 2 and No. 3 are added, 
giving the amounts of feed water consumed per indicated horse¬ 
power per hour, by engines of the class referred to, when in 
good order. The quantities are obtained by computing the 
amount of steam from an indicator diagram corresponding to 
the various cases, and adding the allowance for cylinder 
condensation called for by Table No. 1. Leakage is supposed 
to be entirely absent. 

SAMPLES OF DIAGRAMS USED FOR TABLE NO. 2. 



Figure No. 4. 


The diagrams which are used for these tables are of the form 
represented in Figures No 4 and No. 5, in which a full set is 
given for an initial pressure of 70 lbs. 

The steam line is supposed in these cases to be parallel with 
the atmospheric line up to the point where the cut-off begins. 
The cut-off is taken at the point marked, where the 
pressure is 8 lbs. less than the initial pressure, and the 
percentage of cut-off given refers to the proportion of 
the stroke completed at cut-off. The expansion line lies 



26 


THE TABOR INDICATOR. 


above the hyperbolic curve, drawn through the point of cut¬ 
off, by such an amount that the mean effective pressure less 
the loss produced by the rounding of the diagram at release, is 
increased in the non-condensing table (Table No. 2) at 10$ 
cut-off 0.50 lbs.; at 20$, 0.38 lbs.; at 30$, 0.25 lbs.; at 40$, 
0.12 lbs.; and at 50$, 0 ; and in the condensing table (Table 
No. 3) at 5$ cut-off 0.70 lbs. ; at 10$, 0.60 lbs.; at 15$, 0.52 

SAMPLES OF DIAGRAMS USED FOR TABLE NO. 3. 



Figure No. 5. 


lbs. ; at 20$, 0.45 lbs.; at 30$, 0.30 lbs.; and at 40$, 0.15 lbs. 
The back pressure, which is uniform up to the point of com¬ 
pression. is supposed in the non-condensing table to be 1.3 lbs. 
above the atmosphere or 16 lbs. above zero, and in the condens¬ 
ing table 3.0 lbs. above zero. The compression curve is 
supposed to be hyperbolic and commence at 0.91 of the return 
stroke, with a clearance of 3$ of the piston displacement. 



THE TABOR INDICATOR. 


27 


TABLE No. 2. 

Feed Water Consumption for Non-Condensing Engines. 


Initial pressure above 

Mean effective 

Feed water consumed 

atmosphere. 

pressure. 

per I. H. P. per hour. 

lbs. 

lbs. 

lbs. 

AT 

10 PER CENT. CUT-OFF. 

40 

1.32 

153.24 

50 

5.01 

52.52 

60 

8.70 

37.26 

70 

12.39 

30.99 

80 

16.07 

27.61 

90 

19.76 

25.43 

100 

23.45 

23.90 

AT 

20 PER CENT. CUT-OFF. 

40 

10.22 

38.13 

50 

15.67 

30.98 

60 

21.12 

27.55 

70 

26.57 

25.44 

80 

32.02 

24.04 

90 

37.47 

23.00 

100 

42.92 

22.25 

AT 

30 PER CENT. CUT-OFF. 

40 

16.95 

33.52 

50 

23.71 

29.35 

60 

30.47 

27.24 

70 

37.21 

25.76 

80 

43.97 

24.71 

90 

50.73 

23.91 

100 

57.49 

23.27 

AT 

40 PER CENT. CUT-OFF. 

40 

22.24 

32.79 

50 

29.99 

29.72 

60 

37.75 

27.92 

70 

45.50 

26.66 

80 

53.25 

25.76 

90 

61.01 

25.03 

100 

68.76 

24.47 




































28 


THE TABOR INDICATOR. 


TABLE No. 2.—Continued. 


Initial pressure above 
atmosphere, 
lbs. 

Mean effective 
pressure, 
lbs. 

Feed water consumed 
per I. H. P. per hour, 
lbs. 

AT 

50 PER CENT. CUT-OFF. 


40 

26.40 


33.16 

50 

84.91 


30.53 

60 

43.42 


28.94 

70 

51.94 


27.79 

80 

60.44 


26.99 

90 

68.96 


26.32 

100 

77.48 


25.78 


TABLE No. 3. 

Feed Water Consumption for Condensing Engines. 


Initial presshre above 

Mean effective 

Feed water consumed 

atmosphere. 

pressure. 

per I. H. P. per hour. 

lbs. 

lbs. 

lbs. 


AT 5 PER CENT. CUT-OFF. 


40 

9.34 

18.99 

50 

11.88 

18.51 

60 

14.42 

18.22 

70 

16.96 

17.96 

80 

19.50 

17.76 

90 

22.04 

17.57 

100 

24.58 

17.41 


AT 10 PER CENT. CUT-OFF. 


40 

14.96 

18.25 

50 

18.65 

17.91 

60 

22.34 

17.68 

70 

26.03 

17.47 

80 

29.72 

17.30 

90 

33.41 

17.15 

100 

37.10 

17.02 

































THE TABOR INDICATOR. 


29 


TABLE No. 3— Continued.. 


Initial pressure above 
atmosphere, 
lbs. 

Mean effective 
pressure, 
lbs. 

Feed water consumed 
per I. H. P. per hour, 
lbs. 

AT 15 PER CENT. CUT-OFF 

40 

19.72 

18.41 

50 

24.36 

18.11 

60 

29.00 

17.93 

70 

33.65 

17.75 

80 

38.28 

17.60 

90 

42.92 

17.45 

100 

47.56 

17.32 

AT 20 PER CENT. CUT-OFF. 

40 

23.83 

19.00 

50 

29.28 

18.74 

60 

34.73 

18.98 

70 

40.18 

18.40 

80 

45.63 

18.27 

90 

51.08 

18.14 

100 

56.53 

18.02 

AT 

30 PER CENT. CUT-OFF. 

40 

30.54 

20.57 

50 

37.30 

20.35 

60 

44.06 

20.19 

70 

50.81 

20.04 

80 

57.57 

19.91 

90 

64.32 

19.78 

100 

71.08 

19.67 

AT 

40 PER CENT. CUT-OFF. 

40 

35.84 

21.94 

50 

43.59 

21.76 

60 

51.35 

21.63 

70 

59.10 

21.49 

80 

66.85 

21.36 

90 

74.60 

21.24 

100 

82.36 

21.13 























BO 


THE TABOR INDICATOR. 


CHAPTER VI. 

THE USE OF THE INDICATOR ON LOCOMOTIVES. 

A N important field for the employment of the indicator lies 
in the determination, of the performance of locomotive 
engines. It is important here partly because the indicating of 
locomotives is not commonly practised, and partly because 
locomotives consume a large amount of fuel. The engines of a 
company having 200 miles of road in operation use in the 
neighborhood of 400 tons of coal per day, which at $ 5.00 per 
ton represents the annual expenditure of $ 750 , 000 . If the 
application of the indicator resulted in preventing a waste of 
only 5 per cent, of fuel, it would save to such a company 
$ 37,500 per year. 

It is commonly supposed that serious difficulties interfere 
with the employment of the indicator upon locomotives, and 
this is doubtless one of the main reasons why it is not more 
common. Such difficulties are more fancied than real. If 
the operatoi'’s place is provided with a guard to protect 
him from being thrown from the engine while using his hands 
at the indicator, the process of taking diagrams becomes nearly 
as easy as that of taking them from high speed stationary 
engines. The fact that when suitable provisions are made 
diagrams may be taken from one cylinder at the rate of one 
set. per minute shows that in the matter of manipulation, at 
least, there are no real obstacles. 

To illustrate the benefit that may be derived from the indi¬ 
cating of locomotives, copies of diagrams are appended that 
were taken by the writer on a road that had not hitherto 
employed the indicator. 


THE TABOR INDICATOR. 


31 



Diagram No. 4—Tabor Indicator. 

From Locomotive. Valves set by sound. Speed 208 rev. 
per min. Scale 80. 1st Notch. 



Diagram No. 5—Tabor Indicator. 

From Locomotive. Valves set by sound. Speed 210 rev. 
per min. Scale 80. 3d Notch. 







THE TAfcOR INDICATOR. 


Diagrams No. 4 and No. 5 are from an engine that had 
received the customary adjustment of the valves in the shop ; 
when taken out on the road the engineer thought from the 
sound of the escaping steam that the exhausts were uneven. 
The adjustment was changed till the desired uniformity was 
secured. The diagrams show the manner in which the steam 
was distributed after the change. 

One set was taken when the reversing lever was in the first 
notch ; the other with the lever in the third notch. In one 
set it appears that very little steam was admitted to the 
cylinder on one end, while in the other there is a large differ¬ 
ence in the pressure of admission. That a considerable 
waste of steam was going on here is too apparent to require 
comment. 

There is a marked contrast between these diagrams and 
those numbered 6 and 7, which were taken from an engine 
having more nearly correct adjustment. 



Diagram No. 6—Tabor Indicator. 

From Locomotive. Correct adjustment. Speed, 204 rev. per 
min. Scale 100. 1st Notch. 





THE TABOR INDICATOR. 


33 



Diagram No. 7—Tabor Indicator. 

From Locomotive. Correct adjustment. Speed, 198 rev. per 
min. Scale 100. Between 2d and 3d Notches. 


CHAPTER VII. 


THE METHOD OF INDICATING A STEAM ENGINE. 
HERE are two things to be done in making arrangements 



for indicating a steam engine. The indicator must be 
attached to the cylinder and means provided for giving motion 
to the paper drum. 

To attach the indicator, a hole is drilled at each end of the 
cylinder and tapped for the reception of a half-inch steam 




34 


THE TABOR INDICATOR. 


pipe to which to connect the indicator cock. In horizontal 
engines, the barrel of the cylinder should be selected in 
preference to the heads, as in these positions the indicator can 
be the most easily operated. But wherever attached, it is 
important that the pipe should communicate freely with the 
steam in the cylinder. The hole should not be located, for 
example, in such a position that it is covered by the piston on 
reaching the end of its stroke. The pipes should be short and 
free from unnecessary bends. If a valve is used beneath the 
cock, it should be of the straight way type. It is not best to 
connect the two ends and use a single indicator applied at the 
center. Errors are produced by the long connections and 
increased number of bends that this requires, especially at 
high speeds. If but one indicator is available, it may be used 
alternately, first on one end and then on the other. Should 
there be a necessity for placing the indicator at the center, as 
convenience in operating generally requires in locomotive 
work, the errors due to long connections may be reduced by 
the employment of large pipes and easy bends. 

In drilling and tapping new holes in a cylinder, care should 
be taken that the chips do not enter it, unless they can after¬ 
wards be removed. If no better means can be employed, 
steam may be admitted while the work is going on, and the 
chips blown out as fast as formed. 

Before attaching the indicator, the cock should be opened 
to the atmosphere and the pipes cleared of any loose material 
that may have lodged in them. 

The motion to be given to the paper drum is one that 
coincides on a reduced scale with the motion of the piston of 
the engine. It may be obtained in a variety of ways. The 
ingenuity of the operator will suggest the best plan to be 
followed in any case if he understands the principles. These 
are shown in Figure No. 7, which illustrates one method that 
may be employed for a temporary arrangement. 


THE TABOR INDICATOR. 


35 



The active instrument here concerned is the reducing lever 
A C, which is a strip of pine board three or four inches wide 
and about one and one-half times as long as the stroke of the 
engine. It is hung by a screw or small bolt to a wooden 


















































36 


THE TABOR INDICATOR. 


frame attached overhead. At the lower end a connecting rod, 
C D, about one-third as long as the stroke, is at one end 
attached to the lever, and at the other end to a stud screwed 
into the crosshead, or to an ii*on clamped to the crosshead by 
one of the nuts that adjust the gibs, or to any part of the cross¬ 
head that may be conveniently used. The lever should stand 
in a vertical position when the piston is at the middle of the 
stroke. The connecting rod, when at that point, should be 
about as far below a horizontal position as it is above it at 
either end of the stroke. The cords which drive the paper 
drums may be attached to a screw inserted in the lever 
near the point of suspension, but a better plan is to provide 
a segment, A B, the center of which coincides with the point 
of suspension, and allow the cord to pass around the 
circular edge. The distance from edge to center should 
bear the same proportion to the length of the reducing 

lever as the desired length of diagram bears to the 

length of the stroke. On an engine having a stroke of 48 
inches, the lever should be 72 inches, and the connecting rod 
16 inches in length ; in which case, to obtain a diagram 
4 inches long, the radius of the segment would be 6 inches. 
It is immaterial what the actual length of the diagram is, 
except as it suits the operator’s fancy, but 4 inches is a length 
that is usually satisfactory. It may be reduced to advantage 
to 3 inches at very high speeds. The cords should leave 
the segment in a line parallel with the axis of the cylinder. 
The pulleys over which they pass should incline from a 
vertical plane and point to the indicators wherever they 
may be located. If the indicators and the reducing 

lever can be placed so as to be in line with each other, 

the pulleys may be dispensed with, and the cords carried 
directly from the segment to the instruments, a longer 
arc being provided for this purpose. The arm which holds 
the carrier pulleys on each indicator should be adjusted 
so as to point in the direction in which the cord is received. 



THE TABOR INDICATOR. 


37 


In all arrangements of this kind, the reduced motion is not 
mathematically exact, because the leverage is not constant at 
all points of the stroke. Pantagraph motions have been 
devised for overcoming these defects. Two forms have been 
successfully used, which if well made, well cared for, and 
properly handled, reproduce the motion on the reduced scale 
with perfect accuracy. They are shown in working position 
in Figures No. 8 and No. 9. 



Figure 8 represents the manner of attaching the lazy tongs , 
so called, when the indicators are applied to the side of the 
cylinder. It works in a horizontal plane, the pivot end being 
supported by a post, B, erected in front of the guides, and the 
working end receiving motion from an iron attached to the 
cross-head. By adjusting the post to the proper height and at 
a proper distance in front of the cross-head, the cords may be 
carried from the cord pin, c, to the indicators, without the 
intervention of carrier pulleys. 













































38 


THE TABOR INDICATOR. 



Figure 9 shows a simpler form of pantagraph, for use when 
the indicators are attached to the side of the cylinder. The 
working end, A, receives motion from the cross-head, and the 
foot piece, B, is attached to the floor. The cord pin, D, is 
fixed in line between the pivot and the working end, and 
the pulleys, E, attached to the block, C, guide the cords to 
the indicators. 

The indicator rigging that gives the best results at high 
speeds is a plain reducing lever like that first described, pro¬ 
vided at the lower end with a slot that rides on a stud screwed 
into the cross-head. The length of the lever should be two 
and one-half times the stroke. 

Whatever plan is followed, it is desirable to avoid the use 
of long stretches of cord. If the motion must be carried a 
long distance, strips of wood may often be arranged in their 
place and operated with direct connections. Braided linen 
cord, a little in excess of one-sixteenth of an inch in diameter, 
is a suitable material for indicator work. 

To take a diagram, a blank card is stretched smoothly upon 
the paper drum, the ends being held by the spring clips. The 





































THE TABOR INDICATOR. 


39 


driving cord is attached and so adjusted that the motion of 
the drum is central. The cock is opened to admit steam to 
the indicator till the parts have become heated, which will be 
after a half-dozen revolutions. On being shut off, the pencil 
is brought into contact with the paper, the stop screw is 
adjusted, and a fine clear line traced upon the card. This is 
the atmospheric line. The cock is then opened, and after two 
or three revolutions the pencil is again applied and the 
diagram taken. If it is desired to ascertain the condition of 
the valve adjustment, the pencil needs to be applied only 
while the engine is making one revolution. But to determine 
power it should be applied a longer time, so as to obtain a 
number of diagrams superposed on the same card. The 
fluctuations in the admission of steam, produced by governors 
which do not closely regulate, are so common, that this course 
should always be followed to obtain average results. The 
diagram having been traced and the cock shut, the pencil 
should be applied lightly to the paper to see that the position 
of the atmospheric line remains the same. If a new line is 
traced, it is evidence of error, and the operations should be 
repeated on a new card. 

It is well to mark upon every card the date, time of day, 
and end of the cylinder from which it was taken. In adjust¬ 
ing the valves, the boiler pressure should be observed, and the 
changes that are made before taking a diagram noted on the 
card for reference. If a series of diagrams is being obtained 
for power, they should be numbered in order, and the number 
of revolutions per minute noted either upon every card, or, if the 
speed is nearly constant, upon every other one. If tests are to 
be made for power used by machines or tenants, a number of 
diagrams should be obtained under each condition and the 
results averaged. It is well in these cases to mark each card 
of a set by some letter of the alphabet, and on the first of the 
set specify the machines at the time in operation. 


40 


THE TABOR INDICATOR. 


CHAPTER VIII. 

THE METHOD OF COMPUTING THE HORSE-POWER 
OF AN ENGINE FROM THE INDICATOR DIAGRAM. 

'THE work done by the steam in the cylinder of an engine 
A is measured by the product of the force exerted on the 
piston, into the distance through which the piston moves, and 
is usually expressed by the term foot-pounds. If, for instance, 
a force of 33 lbs. per square inch on a piston having an area 
of 100 square inches is employed to drive the piston 100 times 
over a stroke of 4 feet, the work done by the steam amounts 
to 1.320,000 ft. lbs. The amount of horse-power which the 
steam develops is the number of foot-pounds of work done in 
a minute divided by 33,000. In the example given, the horse¬ 
power developed when 100 strokes are made per minute is 
1,320,000 divided by 33,000 or 40 H. P. 

The force exerted upon the piston is given by the indicator 
diagram, but as it varies in amount at different points of the 
stroke, it is necessary to determine the equivalent force which,, 
acting constantly, would produce the same result. This is 
done by computing from the diagram what is termed the mean 
effective pressure. The product of the mean effective pressure 
expressed in pounds per square inch, the area of the cylinder, 
expressed in square inches ; the length of the stroke, ex¬ 
pressed in feet; and the number of strokes per minute, which 
is twice the number of revolutions per minute, gives the 
number of foot-pounds of work performed per minute. This 
result, divided by 33,000, gives the amount of horse-power 
developed. 


THE TABOR INDICATOR. 


41 


To compute frt>m the diagram the mean effective pressure, 
two lines are drawn perpendicular to the atmospheric line, 
one at each end of the diagram, and the intermediate space 
divided into 10 equal parts, with a perpendicular at each 
point of division. A ready method of performing the 
division is to lay upon the diagram a scale of 10 equal 
parts, the total length of which is a small amount in 
excess of the length of the diagram. It is so placed in a 
diagonal position that the extreme points on the scale lie upon 
the two outside perpendiculars. The desired points may then 
be dotted with a sharp pencil opposite the intermediate divisions 
on the scale. The points where the lines of division cross the 
diagram should be dotted ; and in locating these points they 
should be so placed that the area of the figure enclosed by 
straight lines joining them is exactly equal to the area enclosed 
by the curved line of the diagram. 



Figure No. 10. 





42 


THE TABOR INDICATOR. 


Figure No. 10 shows the extreme perpendiculars A B and 
C D, the intermediate lines of division, the points of inter¬ 
section, and those points which require special location, as, for 
example, the one at E, whicli is so placed that the area 
enclosed by the straight lines, E F and E G, is equal to that 
enclosed by the diagram from F to G. 

The determination of the mean effective pressure consists 
now of finding the average length of the various perpen¬ 
dicular lines included between the points of intersection, 
measured on the scale of the spring. This may be done by 
measuring each line with the scale and averaging the 
results. A better and quicker method is to employ a strip of 
paper, one of the cards upon which a diagram is traced, if 
desired, and mark one after another the various distances on 
its edge, making thereby a mechanical addition, and requiring 
only a final measurement. The,proper course to pursue is to 
lay the edge of the paper on the first line and mark off the 
distance, A H, starting from the end of the paper. Transfer 
the edge of the paper to the last line and add to the first 
measurement the distance, I D. Mark off from the end of the 
paper one-half of the sum of these two distances, and from the 
middle point continue the addition for the intermediate nine 
divisions. When all have been marked, measure with the scale 
of the spring, from the end of the paper to the end of the last 
addition, and divide the result by ten. This gives the mean 
effective pressure. It is essential that one-half the sum of the 
first and last distances be taken, and the sum of this together 
with the intermediate nine be divided by ten. An erroneous 
result is obtained by taking the sum of the whole and dividing 
by eleven. 

In non-condensing engines carrying a light load, the expan¬ 
sion line often extends below the back pressure line and forms 
a loop in the diagram, as shown in Figure No. 11. 


THE TABOR INDICATOR. 


48 



Figure No. 11. 


In computing the mean effective pressure in such cases 
the distances below the back pressure line must be subtracted 
from those above the line. The sum of the first and last 
distances here becomes the difference between the first and last. 

When the mean effective pressure on a large number of 
diagrams is desired, time and labor may be saved by the 
employment of a planimeter, an instrument designed to 
measure the areas of irregular figures. It is operated by 
moving a tracer, with which it is fitted over the line of the 
diagram, and it records the area upon a graduated wheel. 

One of these devices, recently introduced, is the Coffin 
Averaging Instrument illustrated in Figure No. 12. 




44 


THE TABOR INDICATOR, 



Figure No. 12. 

Coffin’s Averaging Instrument, 



















































































































































































































































































































































































































































THE TABOR INDICATOR. 


45 


In using this instrument, the indicator card is placed under 
the clamps with the atmospheric line parallel with the lower 
edge of the stationary clamp, C, and the end of the diagram 
even with the perpendicular edge. The adjustable clamp, K, 
is moved up to the other end of the diagi-am. The block, Q, 
on the instrument being introduced in the groove, I, the tracer, 
O, is set upon the point, D, where the edge of the clamp, L, 
touches the diagram. The graduated wheel is turned so as to 
bring the reading to zero, and the tracer is then moved over the 
line of the diagram in the direction of the motion of the 
hands of a watch, and brought back to its starting point. With 
the eye on the wheel, the tracer is then moved along the edge 
of the clamp till the reading is brought back to zero. The dis¬ 
tance of the point, A, in the position which the tracer now 
occupies to the starting point, D, measured on the scale of the 
spring, is the mean effective pressure. The reading on the wheel 
when the tracer arrives at the starting point is the area of the 
diagram in square inches. From this area the mean effective 
pressure may be computed, if preferred, by multiplying it by 
the quotient obtained by dividing the number of the spring by 
the length of the diagram in inches. 

A skilful operator can work diagrams by the method 
first described, at the rate of twenty per hour. By means of the 
planimeter he can work fifty per hour with the same exertion. 

As an example of the manner of computing the horse¬ 
power of an engine, suppose an engine having a cylinder 15 
inches in diameter, a piston rod 2^ inches in diameter, a 
stroke of 2\ feet, running at a speed of 135 revolutions per 
minute. Suppose the indicator diagrams show a mean effective 
pressure of 36 lbs. per square inch, this being the average of 
the indications at the two ends. The area of the cylinder to 
be used is the net area obtained by deducting one-half the 
area of the rod. The area of a cylinder 15 inches in diameter 
is 176.71 square inches. One-half the area of a rod 2^ inches 
in diameter 2.45 square inches. The net area to be used in 


46 


THE TABOR INDICATOR. 


the computation is 176.71—2.45= 174.26 square inches. 
The speed in feet per minute is 135 X 2^ X 2 = 675 feet. 
The horse-power developed, therefore, is 

36 x 174.26 x 675 4,234,518 

-=-= 128.3 H P. 

33,000 33,000 

The areas of circles of various diameters is given in Table 
No. 4. The rule for computing the area of a circle is to 
square half the diameter and multiply the result by 3.1416. 


✓ 


CHAPTER IX. 

THE METHOD OF COMPUTING THE AMOUNT OF 
STEAM ACCOUNTED FOR BY THE INDICATOR. 

/ T''HE number of cubic feet occupied by the steam in the 
A cylinder at any point of the stroke, and the pressure to 
which it is subjected being known, the number of pounds 
which the steam weighs may be computed. The weight of 
steam at any point less the weight retained in the cylinder at 
compression is the weight accounted for by the indicator. 
The weight accounted for on one stroke, multiplied by the 
number of strokes per hour and divided by the indicated 
horse-power, is the steam accounted for per indicated horse¬ 
power per hour. 





THE TABOR INDICATOR. 


47 


This computation requires a knowledge of the volume of 
the clearance space in the cylinder—that is, the volume of the 
ports and passages which conduct the steam from the admis¬ 
sion valve to the cylinder and from the cylinder to the exhaust 
valve, and the cylindrical space at the end of the cylinder 
between the head and the piston when at the end of its 
stroke. The amount of the clearance in automatic cut-off 
engines built for low speeds varies from 2 per cent, to 5 per 
cent., and in those built for high speeds from 2 per cent, to 
15 per cent. It maybe roughly.determined in any case by 
calculations from measurements of the various spaces. It 
may be accurately determined, when the valves and piston are 
tight, by filling the spaces with water, the amount of which is 
known by previous measurement. 

The volume of the cylinder and the number of strokes are 
concerned in the computation of the actual amount of steam 
accounted for in any given time. So, also, the same are con¬ 
cerned in the calculation of the power developed. For this 
reason it becomes unnecessary to consider these factors when 
only the amount accounted for per horse-power per hour is 
desired This may be accurately and quickly estimated 
directly from the diagram by the use of the formulae : 

13750 * 

M=-—-f( C -f E)W C —(H + E)Whl = 

M. E. P. LV J 

Number of pounds of steam accounted for at cut-off per 
indicated horse-power per hour. 

13750 

N—-r(R+E)W r — (H +E)W h ] = 

M. E. P. 

Number of pounds of steam accounted for at release per indi¬ 
cated horse power per hour. 

[Note. _These formulae are published by permission of Prof. 

Channing Whitaker, of the Mass. Institute of Technology, at whose 
request in 1880 the writer expressed, in this reduced algebraic form, the 
process which had been employed in the Steam Engineering Labora¬ 
tory since its establishment in 1874.] 




48 


THE TABOR INDICATOR. 


In these formulae the symbols stand as follows : 

M. E. P M the mean effective pressure. 

C, the proportion of the direct stroke completed at cut-off. 

E, the proportion borne by the volume of the clearance to 
the volume of the piston displacement—that is, to the 
product of the net area of the cylinder by the stroke. 

R, the proportion of the direct stroke completed at release. 
This is unity when the release occurs at the end of the 
stroke. 

H, the proportion of the return stroke uncompleted at com¬ 
pression. 

Wc, the weight of one cubic foot of steam at the cut-off 
pressure. 

Wh, the weight of one cubic foot of steam at the compres¬ 
sion pressure. 

Wr, the weight of one cubic foot of steam at the release 
pressure. 

The points of cut-off, release and compression referred to, 
are located in the manner directed in Chapter IV. The 
pressures at these points should be taken from zero or a per r 
feet vacuum, which is 14.7 lbs. below the atmosphere when 
the barometer indicates 29.92 inches. If accuracy is desired, 
the height of the barometer should be observed when the 
diagrams are taken and the atmospheric pressure which it 
shows should be used for this purpose. The pressure of the 
atmosphere expressed in pounds per square inch may be 
obtained by multiplying the indication of the barometer by 
the decimal 0.491. 

As an example of the method of calculating the amount of 
steam accounted for by the indicator, the data given by 
Figure No. 8 may be employed. Here the proportions of the 
direct stroke completed at cut-off and release are respectively 
C = 0.808, R — 0.901 ; that of the return stroke uncompleted 
at compression is H = 0.071. The clearance of‘the engine is 
E — 0.02. The pressures above the atmosphere (40 spring) at 


THE TABOR INDICATOR. 


49 


the points of cut-off, release and compression, are respectively 
64.1,13.7, and 3.2,* and above zero 78.8, 28.4, and 17.9. The 
weights of one cubic foot of steam at these pressures are 
respectively W c — 0.1844, Wr = 0.0705, and Wh == 0.0457. 
The mean effective pressure is M. E. P. = 38.45. The steam 
accounted for at the cut-off is then, according to the formulae, 
13750 

M = ~S845 t (0,308 + °- 02 ) 0.1844^(0.071 + 0.02)0.0457] 

13750 13750 

(0.0605 — 0.0042)=- X 0.0563 


38.45 


38.45 


N 


= 20.13 lbs. 

and the steam accounted for at the release is : 

13750 

[(0.91 + 0.02)0.0705 —(0.071 -f 0.02)0.457] 

13750 , 13750 

--(0.0656 — 0.0042) =- X 0.0614 


38.45 


38.45 


21.95 lbs. 


The weights of one cubic foot of steam at various pressures 
are given in Table No. 5, which is copied from D. K. Clark’s 
“ Manual for Mechanical Engineers.” 

The steam accounted for by the indicator should be com¬ 
puted for both the cut-off and the release points of the 
diagram. If the expansion line departs much from the theo¬ 
retical curve, a very different result is shown at one point from 
that shown at the other. In such cases, the extent of the 
loss occasioned by cylinder condensation and leakage is in a 
much more truthful manner indicated at the cut-off than at 
the release. 

*The original of Fig. 3, which was made with a 40 spring, is about 
one-third larger than the printed diagram. 









50 


THE TABOR INDICATOR. 


CHAPTER X. 


THE METHOD OF CONSTRUCTING THE HYPERBOLIC 

CURVE. 


A LTHOUGH little direct information can be gained in 
regard to the economy of an engine by a comparison of 
the hyperbolic curve with the expansion line of the diagram, 
the question of its agreement or departure is an interesting 
one when viewed in connection with the actual performance of 
the engine. 

A method of locating the hyperbolic curve upon the diagram 
is represented in Figure No. 13. 



Figure No. 13, 





THE TABOR INDICATOR. 


51 


Lay off the ordinate O A, or clearance line, at a distance 
from the beginning of the diagram that bears the same pro¬ 
portion to the length of the diagram as the volume of the 
clearance space bears to the piston displacement. Draw the 
line of no pressure, O B, which is 14.7 lbs. below the atmos¬ 
pheric line when the barometer indicates 29.92 At any point, 
C, through which it is desired that the curve shall pass, draw 
the line C E parallel to the atmospheric line, and C D perpen¬ 
dicular to it, and draw from O any lines, O D, O L, O M, 
etc., intersecting them. From the points of intersection, F, 
H, J., etc., erect perpendiculars, and from D, L, M, etc., 
draw lines parallel to the atmospheric line to meet them. 
The intersecting points G, I, K, etc., are points in the desired 
curve. 


CHAPTER XI. 

COMPARISON BETWEEN THE PERFORMANCE OF THE 
TABOR INDICATOR AND THAT OF THE THOMP¬ 
SON AND RICHARDS INDICATORS. 

pOL the purpose of comparing the action of the Tabor 
indicator in practical use with that of the 1 hompson 
and Richards instruments, the writer conducted a test, the 
results of which are seen in the accompanying diagrams, num¬ 
bered from No. 8 to No. 19 inclusive. 

The instruments that were used are those the weights of 
which are given in Chapter II. Neither of them was new or 
specially fitted for the test, but each was in good order. 

The diagrams were all taken from the same engine and the 
same end of the cylinder, and while each set was being 



52 


THE TABOR INDICATOR. 


obtained, the boiler pressure and load were kept practically 
constant. The engine was worked at speeds of 160, 240 and 
300 revs, per min., and a test was made under each condition. 
At the speed of 240 revs, per min. two tests were made with 
different loads. The size of the cylinder of the engine was 
6 inches diam. by 14 inches stroke. 

The diagrams are not exhibited to show excellent engine 
performance, as in the case, for example, of the highest speed, 
it became necessary to work the engine with a very light load; 
but this does not affect the comparison of the different indi¬ 
cators, the object for which the tests were made. It appears 
that in every case the diagrams showed the action of the 
momentum of the pencil movement of the indicator. In the 
case of the Richards indicator, which has the heaviest move¬ 
ment, the fluctuations are very marked. In the Thompson 
instrument they are of much less extent. In the Tabor, 
which has the lightest movement, there is the least amount of 
fluctuation. 

The attainment of smooth diagrams depends somewhat on 
the load upon the engine, the manner in which the steam acts 
in the cylinder, and the condition of the instrument. Such 
diagrams may often be obtained, if the circumstances are favor¬ 
able, even at very high speeds. As examples of excellent 
indicator performance, the diagrams No. 20 to No. 27 are 
appended, all of which were taken with the Tabor Indicator, 
the speeds being noted in the headings. 

The three diagrams, No. 28 to No. 30, were taken from the 
Westinghouse engine with a Tabor Indicator, having a small 
paper drum. These were obtained at speeds of 600, 670 and 
675 revs, per min. respectively. 


[Note.— Diagrams Nos. 18, 19, 20, 23, 24, 25,28, 29 and 30 are full- 
size copies, but the remaining ones are somewhat reduced from the 
originals. They were all reproduced by photo-engraving from care¬ 
ful tracings of the lines marked by the indicators.] 


THE TABOR INDICATOR. 


53 



Diagram No. 8.—Richards Indicator. 

160 revs, per min. 40 spring. 



Diagram No. 9. —Thompson Indicator. 
160 revs, per min. . 40 spring. 






54 


trfE tAfeOE INbtCATOfc. 



Diagram No. 10.— Tabor Indicator. 
160 revs, per min. 40 spring. 





Diagram No. 11. —Richards Indicator. 
240 revs, per min. 40 spring. 






THfc tAfiOR INDICAtOR. 


55 



Diagram No. 12.—Thompson Indicator, 

240 revs, per min. 40 spring. 



Diagram No. 13.— Tabor Indicator. 
240 revs, per min. 40 spring. 






56 


THE TAfcOR INDICATOR. 



Diagram No. 14.' —Richards Indicator. 
240 revs, per min. 40 spring. 



Diagram No.- 15. —Thompson Indicator. 
240 revs, per min. 40 spring. 







THE TABOR INDICATOR. 



Diagram No. 16.—Tabor Indicator. 
240 revs, per min. 40'spring. 



Diagram No. 17— Richards Indicator. 
300 revs, per min. 40 spring. 





58 


THE TABOR INDICATOR. 



Diagram No. 18.—Thompson Indicator, 
300 revs, per min. 40 spring. 



THE TABOR INDICATOR. 


59 



Diagram No. 19.—Tabor Indicator. 
300 revs, per min. 40 spring. 





60 


THE TABOR INDICATOR. 



Diagram No. 20.— Tabor Indicator. 
120 revs, per min. 40 spring. 






61 


THE TABOR INDICATOR. 



Diagram No. 21.— Tabor Indicator. 
120 revs, per min. 40 spring. 



Diagram No. 22.— Tabor Indicator. 
240 revs, per min. 40 spring. 





62 


THE TABOR INDICATOR. 



Diagram No. 23.— Tabor Indicator. 
230 revs, per min. 50 spring. 




Diagram No. 24.— Tabor Indicator. 
240 revs, per min. 50 spring. 



64 


THE TABOR INDICATOR. 



Diagram No. 25.— Tabor Indicator. 
325 revs, per min. 40 spring. 






THE TABOR INDICATOR. 


65 



Diagram No. 26. —Tabor Indicator. 
850 revs, per min. 50 spring. 



Diagram No. 27.— Tabor Indicator. 
350 revs, per min. 50 spring. 





66 


THE TABOR INDICATOR. 



Diagram No. 28.—- 1 Tabor Indicato . 
600 revs, per rain. 80 spring. 



Diagram No. 29.—Taiv»'\ Int icator. 
670 revs, per min. 80 spring. 



Diagram No. 30.—Tabor Indicator. 
765 revs, per min. 80 spring. 






THE TABOR INDICATOR. 


67 


TABLE No. 4. 

Areas of Circles having Diameters varying from 
1 Inch to 100 Inches. 


Diam. 

in 

Inches. 

Area in • 

Square 

Inches. 

Diam. 

in 

Inches. 

Area in 
Square 
Inches. 

Diam. 

in 

Inches. 

Area in 
Square 
Inches. 

1 

0.7854 

3t 3 6 

7.9798 

5^ 

25.967 


0.8866 

3X 

8.2957 

5.X 

27.108 

1 / 

0.9940 

3 in 

8.6180 

6 

28.274 


1.1075 

3X 

8.9462 

6 H 

29.464 

IX 

1.2271 

Q 7 

6 

9.2807 

6 X 

30.679 

lyV 

1.3530 

S'A 

9.6211 

6 X 

31.919 

IX 

1.4848 

Q 9 
^T6 

9.9680 

6 / 

33.183 

1 7 

1.6229 

3/ 

10.320 

6 X 

34.471 

IX 

1.7671 

3 H 

10.679 

6 X 

35.784 

1 * 

1.9175 

3X 

11.044 

6 X 

37.122 

ix 

2.0739 

Q1 3 
^1 6 

11.416 

7 

38.484 

Hi 

2.2365 

3X 

11.793 

7H 

39.871 

i X 

2.4052 

Q1 5 
°T6 

12.177 

?X 

41.282 

lit 

2.5800 

4 

12.566 

m 

42.718 

IX 

2.7611 

4 t V 

12.962 

"X 

44.178 

115 

J-TIf 

2.9483 

4/ 

13.364 


45.663 

2 

3.1416 

4 t 3 6 

13.772 

?X 

47.173 

2yg- 

3.3380 

4/ 

14.186 

7X 

48.707 

2 / 

3.5465 

A 5 
^1 6 

14.606 

8 

50.265 


3.7584 

4X 

15.033 

8 X 

51.848 

2 / 

3.9760 

A 7 
*T 6 

15.465 

8 X 

53.456 

9 5 

4.2000 

4/ 

15.904 

8 X 

55.088 

2 X 

4.4302 

4j 9 6 

16.349 

8 H 

56.745 

' 2 tV 

4.6664 

4/ 

16.800 

8 X 

58.426 

2 / 

4.9087. 

41 1 
“ 1 6 

17.257 

83/ 

60.132 

9 9 
^T<f 

5.1573 

4/ 

17.720 

8 X 

61.862 

2 / 

5.4119 

4ft 

18.190 

9 

63.617 

2ff 

5.6723 

4X 

18.665 

9/ 

65.. 396 

2 / 

5.9395 . 

415 

19.147 

9/ 

67.200 

Ol B 
^T 6 

6.2126 

5 

19.635 

9X 

69.029 

2 X 

6.4918 

5/ 

20.629 

9/ 

70.882 

015 

6.7772 

5X 

21.647 

9/ 

72.759 

3 

7.0686 

5X 

22.690 

9/ 

74.662 

e T V 

7.3662 

5/ 

23 ..758 

9X 

76.588 

3Ji 

7.6699 

5/ 

24.850 

10 

78.540 




























68 


THE TABOR INDICATOR 


TABLE No. 4.—Continued. 


Diam. 

in 

Inches. 

Area in 
Square 
Inches. 

Diam. 

in 

Inches. 

Area in 
Square 
Inches. 

! Diam. 
in 

! Inches. 

! Area in 
Square 

Inches. 

I 

10/8 

80.515 

14/ 

173.782 

1' 19/ 

302.489 

iox 

82.516 

15 

176.715 

19/ • 

306.355 

10 / 

84.540 

15/ 

179.672 

19/ 

310.245 

10 / 

86.590 

15/ 

182.654 

20 

314.160 

10 / 

88.664 

15/ 

185.661 

20 / 

318.099 

10 / 

90.762 

15/ 

188.692 

20 / 

322.063 

10 / 

92.885 

15/ 

191.748 

20 / 

326.051 

13 

95.033 

15X 

194.828 

20 X 

330.064 

11 / 

97.205 

15X 

197.933 

20 X 

334.101 

11 / 

99.402 

16 

201.062 

20 / 

338.163 

11 / 

101.623 

16X 

204.216 

20 / 

342.250 

11 / 

103.869 

16/ 

207.394 

21 

346.361 

11 / 

106.139 

16X 

210.597 

21 / 

350.497 

11 / 

108.434 

16/ 

213.825 

21 / 

354.657 

11 / 

110.753 

16/ 

217.077 

21 / 

358.841 

11 

113.097 

16X 

220.353 

21 / 

363.051 

12 / 

115.466 

16X 

223.654 

21 / 

367.284 

12 / 

117.859 

17 

226.980 

21 / 

371.543 

12 / 

120.276 

17X 

230.330 

21 / 

375.826 

12 / 

122.718 

17 X 

233.705 

22 

380.133 

12 / 

125.184 

17^ 

237.104 

22 / 

384.465 

12 X 

127.676 

17X 

240.528 

22 / 

388.822 

12 / 

130.192 

17X 

243.977 

22 / 

393.203 

13 

132.732 

17X 

247.450 

22 / 

397.608 

13/ 

135.297 

17X 

250.947 

22 / 

402.038 

13X 

137.886 

18 

254.469 

22 / 

406.493 

13/ 

140.500 

18 H 

258.016 

22 / 

410.972 

13/ 

143.139 

18 X 

261.587 

23 

415.476 

13/ 

145.802 

18 X 

265.182 

23/ 

420.004 

v&U 

148.489 

18X 

268.803 

23X 

424.557 

13/ 

151.201 

18/ 

272.447 

23/ 

429.135 

14 

153.938 

18/ 

276.117 

23/ 

433.731 

14/ 

156.699 

18X 

279.811 

23/ 

438.363 

14X 

159.485 

19 

283.529 

23/ 

443.014 

14/ 

162.295 

19/ 

287.272 

23/ 

447.699 

MX 

165.130 

1»X 

291.039 

24 

452.390 

14/ 

167.989 

19/ 

294.831 

24/ 

457.115 

14X 

170.873 

19/ 

298.648 

24/ 

461.864 





























THE TABOR INDICATOR. 


69 


TABLE No. 4—Continued. 


Diam. 

in 

Inches. 

Area in 
Square 
Inches. 

Diam. 

in 

Inches. 

Area in 
Square 
Inches. 

Diam. 

in 

Inches. 

Area in 
Square 
Inches. 

243/ 8 

466.638 

29 / 

666.227 

87 / 

1119.24 

24 / 

471.436 

29 / 

671.958 

88 

1134.11 

24 /s 

476.259 

29 / 

677.714 

■sax 

1149.08 

24 / 

481.106 

29 / 

683.494 

88/ 

1164.15 

24 /s 

485.978 

29 / 

689.298 

88/ 

1179.32 

25 

490.875 

293 / 

695.128 

39 

1194.50 

25 % 

495.796 

29 / 

700.981 

89 / 

1209.95 

25 / 

500.741 

30 

706.860 

89 / 

1225.42 

253 / 

505.711 

30X 

718.690 

89 / 

1240.08 

25 / 

510.706 

80 / 

730.618 

40 

1256.60 

253/s 

515.725 

803 / 

742.644 

40 / 

1272.39 

253 / 

520.769 

31 

754.769 

40 / 

1288.25 

25 /s 

525.837 

81 / 

766.992 

40 / 

1304.20 

26 

530.930 

81 / 

779.313 

41 

1320.25 

26 /s 

536.047 

81 / 

791.732 

41/ 

1336.40 

26 / 

541.189 

82 

804.249 

41 / 

1352.65 

26 /s 

546.356 

32 X 

816.865 

41 / 

1369.00 

26 / 

551.547 

S 2/ 2 

829.578 

42 

1385.44 

26 /s 

556.762 


842.390 

42 / 

1401.98 

263 / 

562.002 

33 

855.30 

42 / 

1418.62 

26 /s 

567.267 

33X 

868.30 

42 / 

1435.56 

27 

572.556 

33 % 

881.41 

43 

1452.20 

27 / 

577.870 

333^ 

894.61 

' 48 / 

1469.13 

27 / 

583.208 

34 

907.92 

48 / 

1486.17 

27 H 

588.571 

34X 

921.32 

48 / 

1503.30 

27 / 

593.958 

84 / 

934.82 

44 

1520.53 

273 /s 

599.370 

84 / 

948.41 

44 / 

1537.86 

273 / 

604.807 

35 

962.11 

44 / 

1555.28 

27 /s 

610.268 

35X 

975.90 

44 / 

1572.81 

28 

615.753 

85 / 

989.80 

45 

1590.43 

28 / 

621.263 

85 / 

1003.78 

45 / 

1608.15 

28 / 

626.798 

36 

1017.87 

45 / 

1625.97 

28 / 

632.357 

56 X 

1032.06 

45 / 

1643.89 

28 / 

637.941 

36^ 

1046.35 

46 

1661.90 

28 / 

643.594 

86/ 

1060.73 

46 / 

1680.01 

28 3 / 

649.182 

37 

1075.21 

46 / 

1698.23 

28 /s 

654.839 

87 / 

1089.79 

46 / 

1716.54 

29 

660.521 

87 / 

1104.46 

47 

1734.94 


















70 


THE TABOR INDICATOR. 


TABLE No. 4—Continued. 


Diam. 

in 

Inches. 

Area'in 
Square 
Inches. 

Diam. 

in 

Inches. 

Area in 
Square 
Inches. 

Diam. 

in 

Inches. 

Area in 
Square 
Inches. 

47 % 

1753.45 

59 

2733.97 

73 y 

4242.92 

47 

1772.05 

59^ 

2780.51 

74 

4300.85 

47^ 

1790.76 

60 

2827.44 

74 % 

4359.16 

48 

1809.56 

60^ 

2874.76 

75 

4417.87 

48X 

1828.46 

61 

2922.47 

76 

4536.47 

48 % 

1847.45 

61 X 

2970.57 

77 

4656.63 

48 % 

1866.55 

62 

3019.07 

78 

4778.37 

49 

1885.74 

62K 

3067.96 

79 

4901.68 

49^ 

1905.03 

63 

3117.25 

80 

5026.56 

49^ 

1924.42 

63^ 

3166.92 

81 

5153.00 

49^ 

1943.91 

64 

3216.99 

82 

5281.02 

50 

1963.50 

64^ 

3267.46 

83 

5410.62 

50 % 

2002.96 

65 

3318.31 

84 

5541.78 

51 

2042.82 

65^ 

3369.56 

85 

5674.51 

51 % 

2083.07 

66 

3421.20 

86 

5808.81 

52 

2123.72 

66'A 

3473.23 

87 

5944.69 

52^ 

2164.75 

67 

3525.62 

88 

6082.13 

53 

2206.18 

67^ 

3578.47 

89 

6221.15 

53K 

2248.01 

68 

3631.68 

90 

6361.74 

54 

2290.22 

68 yi 

3685.29 

91 

6503.89 

54 yi 

2332.83 

69 

3739.28 

92 

6647.62 

55 

2375.83 

69^ 

3793.67 

93 

6792.92 

55 % 

2419.22 

70 

3848.46 

94 

6939.79 

56 

2463.01 

70 ^ 

3903.63 

95 

7088.23 

56 K 

2507.19 

71 

3959.20 

96 

7238.24 

57 

2551.76 

ny 2 

4015.16 

97 

7389.80 

57^ 

2596.72 

72 

4071.51 

98 

7542.96 

58 

2642.08 

72 ^ 

4128.25 

99 

7697.68 

5 8/ 2 

2687.83 

73 

4185,39 

100 

7854.00 






























:r s< 

ab( 

ero 

lbs. 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

12 

13 

14 

14 

15 

16 

17 

18 

19 

20 

21 

22 

23 

24 

25 

26 

27 

28 

29 

30 

31 

82 


THE TABOR INDICATOR. 


71 


TABLE No . 5. 

Properties of Saturated Steam. 
(From D. K. Clark’s “Manual.”) 


mperature 

in 

ahrenheit 

Degrees. 

Total Heat in 
Fahrenheit 
Degrees 
above zero. 

Weight of 
one cubic foot 
of steam 
lbs. 

Weight 
of one 
cubic 
foot of 
water 
lbs. 

102.1 

1144.5 

.0030 

62.00 

126.3 

1151.7 

.0058 

— 

141.6 

1156.6 

.0085 

— 

153.1 

1160.1 

.0112 

61.14 

162.3 

1162.9 

.0138 

— 

170.2 

1165.3 

0163 

— 

176.9 

1167.3 

.0189 

60.62 

182.9 

1169.2 

.0214 

— 

188.3 

1170.8 

.0239 

— 

193.3 

1172.3 

.0264 

— 

197.8 

1173.7 

.0289 

60.03 

202.0 

1175.0 

.0314 

— 

205.9 

1176.2 

.0338 

— 

209.6 

1177.3 

.0362 

— 

212.0 

1178.1 

.0380 

59.64 

213.1 

1178.4 

.0387 

— 

216.3 

1179.4 

.0411 

— 

219.6 

1180.3 

.0435 

— 

222.4 

1181.2 

.0459 

— 

225.3 

1182.1 

.0483 

59.46 

228.0 

1182.9 

.0507 

— 

230.6 

1183.7 

.0531 

— 

233.1 

1184.5 

.0555 

— 

235.5 

1185.2 

.0580 

— 

237.8 

1185.9 

.0601 

59.10 

240.1 

1186.6 

.0625 

— 

242.3 

1187.3 

.0650 

—. 

244.4 

1187.8 

.0673 

—- 

246.4 

1188.4 

.0696 

— 

248.4 

1189.1 

.0719 

-3 

250.4 

1189.8 

.0743 

58.74 

252.2 

1190.4 

.0766 

— 

254.1 

1190.9 

.0789 

— 













72 THE TABOR INDICATOR. 


TABLE No. 5—Continued. 


Total 
Pressure 
per sq. 
in. above 
zero, 
lbs. 

Temperature 

in 

Fahrenheit 

Degrees. 

Total Heat in 
Fahrenheit 
Degrees 
above zero. 

Weight of 
one cubic foot 
of steam, 
lbs. 

Weight 
of one 
cubic 
foot of 
water 
lbs. 

38 

255.9 

1191.5 

.0812 

_ 

34 

257.6 

1192.0 

.0835 

— 

35 

259.3 

1192.5 

.0858 

— 

36 

260.9 

1193.0 

.0881 

— 

37 

262.6 

1193.5 

.0905 

58.39 

38 

264.2 

1194.0 

.0929 

— 

39 

265.8 

1194.5 

.0952 

— 

40 

267.3 

1194.9 

.0974 

— 

41 

268.7 

1195.4 

.0996 

— 

42 

270.2 

1195.8 

.1020 

— 

43 

271.6 

1196.2 

.1042 

— 

44 

273.0 

1196.6 

.1065 

— 

45 

274.4 

1197.1 

.1089 

— 

46 

275.8 

1197.5 

.1111 

58.03 

47 

277.1 

1197.9 

.1133 

— 

48 

278.4 

1198.3 

.1156 

_ 

49 

279.7 

1198.7 

.1179 

_ 

50 

281.0 

1199.1 

.1202 

_ 

51 

282.3 

1199.5 

.1224 

_ 

52 

283.5 

1199.9 

.1246 

_ 

53 

284.7 

1200.3 

.1269 

_ 

54 

285.9 

1200.6 

.1291 

_ 

55 

287.1 

1201.0 

.1314 

_ 

56 

288.2 

1201.3 

.1336 

57.65 

57 

289.3 

1201.7 

.1358 


58 

290.4 

1202. 

.1380 

. 

59 

291.6 

1202.4 

.1403 

_ . 

60 

292.7 

1202.7 

.1425 

_ 

61 

293.8 

1203.1 

.1447 

_ 

62 

294.8 

1203.4 

.1469 

—— 

63 

295.9 

1203.7 

.1493 

— 

64 

296.9 

1204.0 

.1516 

. 

65 

298.0 

1204.3 

.1538 


66 

299.0 

1204.6 

.1560 


67 

300.0 

1204.9 

.1583 

57.29 

68 

300.9 

1205.2 

.1605 

— 












THE TAfcOR INDICATOR. 


73 


TABLE No. 5—Continued. 


Total 
Pressure 
per sq. 
in. above 
zero, 
lbs. 

Temperature 

in 

Fahrenheit 

Degrees. 

Total Heat in 
Fahrenheit 
Degrees 
above zero. 

Weight of 
one cubic foot 
of steam, 
lbs. 

Weight 
of one 
cubic 
foot of 
water, 
lbs. 

69 

301.9 

1205.5 

.1627 

__ 

70 

302.9 

1205.8 

.1648 

— 

71 

303.9 

1206.1 

.1670 

— 

72 

304.8 

1206.3 

.1692 

— 

73 

305.7 

1206.6 

.1714 

— 

74 

306.6 

1206.9 

.1736 

— 

75 

307.5 

1207.2 

.1759 

— 

76 

308.4 

1207.4 

.1782 

— 

77 

309.3 

1207.7 

.1804 

- . 

78 

310.2 

1208. 

.1826 

57.01 

79 

811.1 

1208.3 

.1848 

— 

80 

312.0 

1208.5 

.1869 

— 

81 

312.8 

1208.8 

.1891 

— 

82 

313.6 

1209.1 

.1913 

— 

83 

314.5 

1209.4 

.1935 

— 

84 

315.3 

1209.6 

.1957 

— 

85 

316.1 

1209.9 

.1980 

— 

86 

316.9 

1210.1 

.2002 

— 

87 

317.8 

1210.4 

.2024 

- - 

88 

318.6 

1210.6 

.2044 

— 

89 

319.4 

1210.9 

.2067 

— 

90 

320.2 

1211.1 

.2089 

56.75 

91 

321.0 

1211.3 

.2111 

— 

92 

321.7 

1211.5 

,2133 

— 

93 

322.5 

1211.8 

.2155 

— 

•94 

323.3 

1212.0 

.2176 

— 

95 

324.1 

1212.3 

.2198 

— 

96 

324.8 

1212.5 

.2219 

-- 

97 

325.6 

1212.8 

.2241 

— 

98 

326.3 

1213.0 

.2263 

-- 

99 

327.1 

1213.2 

.2285 

— 

100 

327.9 

1213.4 

.2307 

— 

101 

328.5 

1213.6 

.2329 

— 

102 

329.1 

1213.8 

.2351 

— 

103 

329.9 

1214.0 

.2373 

56.39 

m 

330.6 

1214.2 

.2393 

— 




















THE TABOft INDICATOR. 


74 


TABLE No. 5—Continued. 


Total 
Pressure 
per sq. 
in. above 
zero, 
lbs. 

Temperature 

in 

Fahrenheit 

Degrees. 

Total Heat in 
Fahrenheit 
Degrees 
above zero. 

Weight of 
one cubic foot 
of steam, 
lbs. 

Weight 
of one 
cubic 
toot of 
water, 
lbs. 

105 

331.3 

1214.4 

.2414 

_ 

106 

331.9 

1214.6 

.2435 

— 

107 

332.6 

1214.8 

.2456 

— 

108 

333.3 

1215.0 

.2477 

— 

109 

334.0 

1215.3 

.2499 

— 

110 

334.6 

1215.5 

.2521 

— 

111 

335.3 

1215.7 

.2543 

— 

112 

336.0 

1215.9 

.2564 

— 

118 

336.7 

1216.1 

.2586 

— 

114 

337.4 

1216.3 

.2607 

— 

115 

338.0 

1216.5 

.2628 

— 

116 

338.6 

1216.7 

.2650 

— 

117 

339.3 

1216.9 

.2672 

— 

118 

339.9 

1217.1 

* .2694 

56.09 

119 

340.5 

1217.3 

.2715 

— 

120 

341.1 

1217.4 

.2738 

_ 

121 

341.8 

1217.6 

.2759 

_ 

122 

342 4 

1217.8 

.2780 

_ 

128 

343.0 

1218.0 

.2801 

_ 

124 

343.6 

1218.2 

.2822 

— 

125 

344.2 

1218.4 

.2845 

_ 

126 

344.8 

1218.6 

.2867 

_ 

127 

345.4 

1218.8 

.2889 

_ 

128 

346.0 

1218.9 

.2911 

- 

129 

846.6 

1219.1 

.2933 

_ 

130 

347.2 

1219.3 

.2955 

_ 

131 

347.8 

1219.5 

.2977 

_ 

132 

348.3 

1219.6 

.2999 

_ 

133 

348.9 

1219.8 

.3020 

_ 

134 

349.5 

1220.0 

.3040 

_ 

135 

350.1 

1220.2 

.3060 

55.79 

136 

350.6 

1220.3 

.3080 


137 

851.2 

1220.5 

.3101 

_ 

138 

351.8 

1220.7 

.3121 

_ 

139 

852.4 

1220.9 

.3142 

_ 

140 

352.9 

1221.0 

.3162 

— 














tttfc TAfcOfc INDICATOR. 


75 


TABLE No. 5—Continued. 


Total 
Pressure 
per sq. 
in. above 
zero, 
lbs. 

Temperature 

in 

Fahrenheit 

Degrees. 

Total Heat in 
Fahrenheit 
Degrees 
above zero. 

Weight of 
one cubic foot 
of steam, 
lbs. 

Weight 
of one 
cubic 
foot of 
water, 
lbs. 

141 

353.5 

1221.2 

.3184 

_ 

142 

354.0 

1221.4 

.3206 

— 

143 

354.5 

1221.6 

.3228 

— 

144 

355.0 

1221.7 

.3250 

— 

145 

355,6 

1221.9 

.3273 

— 

146 

356.1 

1222.0 

.3294 

— 

147 

356.7 

1222.2 

.3315 

— 

148 

357.2 

1222.3 

.3336 

— 

149 

357.8 

1222.5 

.3357 

— 

150 

358.3 

1222.7 

.3377 

55.54 

160 

363.4 

1224.2 

.3590 

— 

170 

368.2 

1225.7 

.3798 

— 

180 

372.9 

1227.1 

.4009 

— 

190 

377.5 

1228.5 

.4222 

— 

200 

381.7 

1229.8 

.4431 

— 












76 


THE 

ASHCROFT MANUFACTURING CO. 


Factories: BOSTON AND LYNN. 


Office and Salesrooms: III Liberty St., New York Cify. 

MANUFACTURERS OF 

THE TABOR STEAM ENGINE INDICATOR, 

Pantographs, Planimeters and Three-way Cocks, 
Steam Vacuum Pressure and Test Gauges, 
Packer Ratchet Drills, 

Brown’s Adjustable Pipe Tongs, 
Pipe Stocks and Dies, 

Revolution Counters, 

Locomotive and Marine Clocks, 

Siphon Cocks, 

Water Gauges and Columns, 
Self-cleaning and Patent Handle Gauge Cocks, 
Safety Valves, 

Locomotive Spring Balances, 

Plain, Enameled and Fused End, 
Water Gauge Glasses, 

Combination Engine Room 

Sets of Instruments. 




77 


T ZEE IE 

ASHCROFT MANUFACTURING CO., 

MANUFACTURERS OF 

Moscrop’s Continuous Recorder for Steam Engines, 
Low Water Detectors and Alarms, 

Patent Oil Testing Machines, 

Steam Whistles and Gong Bells, 
Screw and Lever Hydraulic Test Pumps, 

Gasfitters’ Proving Pumps and Gauges, 
Lubricators and Plain Oil Cups, 

Pyrometers and Thermometers, 
Saunder’s Patent Corrugated Copper Packing, 
Inspectors’ Test Pumps and Gauges, 

Mercury Columns, 

McCracken Patent Steam Traps, 

Boiler Feed Pumps—Hand, Pulley and Direct 
Acting. 

Martin’s Patent Balanced Furnace Doors and 
Patent Grate Bars. 


78 


The Consolidated Safety Valve Co. 

Manufacturers of the only 

NICKEL-SEATED POP SAFETY YALYE 

— IB 1 O IR, — 

LOCOMOTIVES, 

FARM ENGINES, 

STATIONARY BOILERS, 
MARINE BOILERS, 

Single and Duplex Patterns, 
Snifting Valves for Engines, 
Water Relief Valves for Water Works, 

and for all purposes where Perfect Safety 
is desired. These patents cover all Safety 
Valves utilizing the Recoil Action of 
Steam. _ 


OFFICE AND SALESROOMS: 

111 LIBERTY STREET 
NEW YORK CITY. 



79 


H. S. MANNING. E. L. MAXWELL. C. A. MOORE. 

MANNING, MAXWELL A MOORE, 

111 LIBERTY STREET, 

NEW YORK CITY. 

Manufacturers of and Dealers in all kinds of 

Railway and Machinists’ 
Tools and Supplies. 

We are prepared to furnish all 
hinds of Railroad Equipment, and 
to arrange and submit plans for 
shops, and make estimates for the 
tools, showing their foundations and 
distribution in shops. 

Foundries, Machine and Carpen¬ 
ter Shop plants. 





80 


.A-GKEHNTC1T OF TZE3IF 

Niles Tool Works, 

MANUFACTURERS OF 

Single and Double Axle Lathes, 

Arch Bar Drilling Machines, 6 or 8 Spindle, 
Horizontal Boring and Drilling Machines, 

Wheel Borers with Cranes, 

Boring and Turning Mills, 5 to 16 feet. 

Bending Rolls and Plate Planers, 

Cylinder Borers, 

Radial and Upright Drill Presses. 

Rail and 8 Spindle Drill Presses, 

Driving Wheel Lathes, 

Hydrostatic Wheel Presses, 

Engines Lathes, 26 to 60 inches swing, 

Special Pulley Turning and Boring Machinery, 
Planers,-26 to 72 inches, square, 

Quartering Machines for Locomotive Drivers, 
Shafting Lathes, 

Shapers, 14, 16 and 24 inch Stroke, 

Slotters, 9, 13 and 18 inch Stroke, 


MANNING, MAXWELL & MOORE, 

I I I Liberty St., New York City. 



81 


HST03T OIF 1 THE 

Morgan Engineering Co.’s 

Steam Hammers, Double and Single Stand, from 
150 to 4,500 pounds. 

Also Drop and Helve Hammers of all sizes, and 
adapted to any kind of work. 

Boiler Rolls and Steam Riveters, 

Plate Punches with Spacing Attachments, Alligator 
Shears. 

The Long & Alstatter Co.’s 

Power Punches and Shears, makers of all sizes, 
punching from 3^4 inch diam. hole, 1 % deep, 
and Shearing from 10x1^ to small holes and 
thin sheets. 

Adjustable Helve Hammers, 

Novelty Iron Works’ 

Acme Bolt Cutters, Tappers, Bolt Headers, &c. 


MANNING, MAXWELL & MOORE, 

I I I Liberty St., New York City. 



82 


AGENCY OF THE 

Brainard Milling Machine Co. 

MANUFACTURERS OF 

Plain, Standard and Universal Millers, 

Spiral Cutters, Milling Machine Vises, 

Universal Heads, 

Patent Back Centers, 

Gear Cutters, Plain and Automatic, 

Milling Cutters and Mill Grinders, 

Steel Bar Bench Vises. 

F. E. Reed’s 

Engine Lathes, 11 inch swing and upward, 

Engine Foot Lathes, n and 12 inch swing, 
Speed or Hand Lathes, 9 to 16 inch swing, 

Bench Hand Lathes, 

Drill Presses, Lever and Wheel Feed, from 18 to 
2.2 inch swing. 

Prentice Bros.’ 

Upright Drills, Back Geared, Self Feed, and 
Wheel and Lever Feeds, from 12 to 36 inch 
swing. 

MANNING, MAXWELL & MOORE, 

I I I Liberty St., New York City. 



-A-G-ZEirSTOTT OF TZE3CF 

Morse Twist Drill & Machine Co. 

For sale of their entire output of Machinists,’ Nut, 
Blacksmiths’ and Machine Screw, Boiler and 
Pipe Taps, Bolt Dies, Adjustable Dies, Screw 
Plates, Tap Wrenches, &c., &c. 

Worcester Machine Screw Co.’s 

Steel and Case Hardened Milled Set Screws, 

Square and Hexagon Head Milled Cap Screws, 
Round, Flat and Fillister Head Machine Screws, 
Finished and Rough Body Milled Studs. 

Hoopes & Townsend’s 

Machine Bolts, Lag Screws, Bolt Ends, 

Cold Pressed Square and Hexagon Nuts, 

Plate Washers, 

Boiler, Bridge and Tank Rivets, 

Track Bolts, Turn Buckles and Pipe Swivels, 
Punched Link Chains, 

Bridge and Roof Irons, 

Patch Bolts. 


MANNING, MAXWELL & MOORE, 

I I I Liberty St., New York City. 



84 


MANNING, MAXWELL & MOORE, 

Agents for 

Midvale Steel Co.’s Tires, Axles, Forg¬ 
ings and Castings. 

Colliau Furnace Co.’s Patent Cupolas. 
Standard Tube Welder. 

Jenne Track Jacks. 

I X L Track Drills. 

Huntington Track Gauges. 

Brady Emery Grinding Machinery. 
Bradlee & Co.’s Chains and Cables. 
Hancock Inspirator Co. 

Keystone Portable Forge Co. 
Westcott’s Lathe and Drill Chucks. 
Prouty’s Planer Chucks. 

Smith’s Hub Friction Clutches • and 


Pulleys. 



* 


, 













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» 



1 



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